This invention relates generally to methods and apparatus for infusing liquids into bone trabecula and/or aspirating bone marrow and, more particularly, to such methods and apparatus in which the depth of entry into the bone is carefully controlled.
Drugs and other liquids are customarily delivered to patients via their vascular systems, using a needle or catheter inserted into a peripheral blood vessel. Such techniques function generally satisfactorily in cases where the patient's blood pressure is at normal levels. However, in cases where the patient is in circulatory shock due to heart failure, drug overdose, or severe hemorrhaging, the peripheral blood vessels frequently are collapsed and access to those blood vessels can be difficult. Peripheral vessel catherization also is exceedingly difficult in pediatric patients because of the small size of their peripheral vessels. Substantial delays in administrating the drugs and liquids can therefore result and, in many instances, vascular access cannot be attained at all. Severe injury to the patient, even death, can therefore result.
In such cases of serious circulatory shock and hemorrhaging, one suitable alternative to vascular infusion is intraosseous infusion. In particular, the resuscitative fluid or drug solution is injected directly into the relatively porous trabecula of the patient's bone. Typically, the sternum, femur, tibia, or other long bone located near the skin is used. Intraosseous infusion also is sometimes used on newborns and small children when suitable blood vessels cannot easily be accessed. Intraosseous infusion requires the penetration by a needle or the like of the patient's skin and outer cortical bone, to gain access to the trabecular bone.
Another need for accessing the trabecular bone arises when a bone marrow sample is to be drawn, or aspirated. Again, a needle or the like must penetrate the patient's skin and outer cortical bone to gain access to the trabecular bone.
Although intraosseous infusion is considered a viable alternative to vascular infusion, it has not met with widespread acceptance. One reason for this is the practical difficulty of penetrating the infusion needle or other device to the proper depth in the bone. Typically, a collar or other stop is fixed on the needle shaft to indicate when the needle has penetrated to a particular depth that is estimated to be within the trabecular bone. This technique is not always effective, however, because it relies on a mere estimate of the required depth and because patients' internal bone structure can vary significantly. These same difficulties apply to the aspirating of bone marrow samples, as well.
Monitoring the resistance to penetration of a conventional infusion or aspiration needle is not always an effective indicator of the needle's position within the bone, either. Generally speaking, the resistance is relatively high when the tip of the needle is moving through the outer cortical bone, and it decreases when the tip reaches the trabecular bone. The resistance increases again if the needle tip reaches the inner cortical bone, on the opposite side of the trabecula. However, such variations in resistance can be very subtle and can vary substantially from one patient to another. Accordingly, monitoring penetration resistance is not considered a completely effective technique for controlling penetration depth.
It should therefore be appreciated that there is a significant need for an intraosseous infusion or aspiration apparatus, and related method, that conveniently and accurately places the tip of an infusion/aspiration needle or tube within a patient's trabecular bone, for an effective infusion of liquid to, or aspiration of bone marrow from, a patient. The present invention fulfills this and other important needs.